1. Field of the Invention
This invention relates to compositions of matter containing dyes that are not visible to the naked eye when in solution but which fluoresce when illuminated by ultra-violet light, thereby making them visible. In particular, this invention relates to compositions of matter containing aqueous corrosive fluoride solutions and a dye that fluoresces in the visible region when illuminated by ultra-violet light.
2. Description of the Prior Art
Aqueous etchant solutions of a type regularly used in semiconductor manufacture to etch wafers, e.g., silicon wafers, contain up to fifty percent by weight of corrosive fluoride compounds, particularly hydrofluoric acid (HF) and/or ammonium fluoride (NH.sub.4 F). A "corrosive fluoride" compound is defined herein as a fluoride compound that adversely affects human skin after contact. These compounds, particularly hydrofluoric acid, are not readily detected if accidentally gotten on the skin, work surfaces or clothing and once on the skin, can cause very painful burns several hours later. Prompt injection of calcium compounds is necessary to counteract the fluoride ion and avoid injury. An easy and rapid way of detecting corrosive fluoride solutions on work surfaces, clothing or human skin is therefore highly desirable.
There have been ways suggested in the past of making various compounds visible by dying them. One example is U.S. Pat. No. 3,737,349, issued June 5, 1973, to Michael K. Levenson. This disclosure teaches the use of a fluorescing compound in an explosive composition, which may leak or be extruded from its casing. The fluorescent compound provides a way of detecting the particular leaking explosive casing.
U.S. Pat. No. 2,325,421, issued July 27, 1943, to Allen L. Omohundro, et al., teaches the identification of white mineral oils by adding very small amounts of carotene compounds.
U.S. Pat. No. 2,267,758, issued Dec. 30, 1941 to Francio M. Sell shows a variety of dyes that can be used to invisibly mark textiles. The dyes are made visible under ultra-violet illumination.
U.S. Pat. No. 4,231,750, issued Nov. 4, 1980 to Robert M. Dawben, et al., shows a method of fluoroimmunioassay. A fluorescently labeled low molecular weight antigen is used to assay small amounts of enzymes.